In countries where winter is cold, such as Canada, mechanics in motor vehicle repair shops need to work inside a heated closed garage, often having only minimal ventilation means. In a closed garage, when a mechanics works on a motor vehicle having its engine running, it is essential that the combustion gases be brought to the outside of the garage, otherwise, the mechanics would become intoxicated by carbon monoxide.
Usually, this evacuation is effected by simply slipping an elongated rubber hose at one end onto the motor vehicle exhaust pipe, and extending the opposite end portion of the rubber hose under or through a hole in the garage door.
An accidental slight pull will cause the rubber hose to disengage from the exhaust pipe and combustion gases will escape into the garage. Even when the rubber hose remains connected to the metal exhaust pipe, some combustion gases may find their way out from the inner mouth of that rubber hose, into the garage. The rubber hose may also deteriorate by melting at its portion in direct contact with the hot tail pipe.